Newbie needs micrometer help
Just picked up a used mike for cheap and need a little help.
It's a Mitutoyo 0-1", No. 293-832
The digital readout can be zeroed and is right on, but the thimble is 0.025" off to the negative (ie. when the thimble reads 0.000, I still have a 0.025" gap at the anvil). I really hope the U-frame is not sprung.
I do not have the instruction manual or the little wrench that usually comes with a mike and my Google-fu must be lacking because I can't find a manual anywhere on the Intertoobs.
Does anyone have a manual or know how I can zero the thimble?
Last edited by kyfho; 09-23-2010 at 08:26 PM.
On all my cheap chinese $20 micrometers its as simple as taking the little pin wrench and rotating the spindle in the light press fiting. But iv never done it because they are all dead on.
Isent 0.025" one revolution btw? Sure your not just reading it wrong? Afaik when its at 0, you really can't see most of the 0 and the 0 line is pertty much covered.
If the caliper was 'sprung' out, the jaws would no longer be parallel btw.. And I think it would have drop dents/scratchs if enough force ever hit it to spring it 0.025" unless the pervious owner tryed to use it as a C clamp.
There should be a wrench with your other Mic's that will enable you to rotate the barrel so readings will coincide.
There will be a pinhole at the base of the barrel that will allow you to rotate the marked definitions on the barrel so they will agree.
Mic a known Dia for verifacitation.
(1/2 dowel pin = .50025 , .5003 +- ?)
Piece white paper gently close mike onto it and pull papaer out. Might be shmeg on the Mike tips. Always check for clean tips. Just a TIP. Mike
If it was sprung 25 mils the anvils wouldn't be way out of parallel and it would be pretty obvious. Somebody spun the barrel a full turn or disassembled and reassembled slightly incorrectly.
It is nice that it still has the analog graduations. Some of them don't.
If you don't have the spanner, you could improvise one.
I don't think its your google-fu, Mitutoyou isn't good about manuals. Apparently, the aspire to provide service as bad as the chinese.
Looks to me like it has been assembled incorrectly. 0.025" is one full turn of the barrel,so try taking it to bits and putting it back together correctly.
The barrel may not be seated fully against the micrometer body. See if there is a gap. It would be hard to shove it back in place, but easier to use the adjustment spanner and rotate it back in place.
+1 to this. I have one of those micrometers shown in the photo in the 1" to 2" size range, and it's dead-on everywhere. When I check it using the 1" standard, the thimble just covers the first line, barely. I can still see some of the line, but mostly it's covered.
Originally Posted by Black_Moons
I would not adjust ANYTHING until you've gotten a 2nd opinion. Have an experienced machinist or 3 look it over.
Thanks for the input, guys. I found a spanner from another mic and used it to turn the barrel in by .025 (1 full turn) and it lines up dead on now.
Sorry for the lame question. I have had to adjust a barrel before, but only by a half thou or so. Never had one this far out. I didn't know that the barrel is threaded also. I just thought it spun around in the same plane, not in & out.
Now I just need to pick up some batteries.